Integrated Electronic Switch and Control Module for a Power Tool

ABSTRACT

An electronic switch and control module for a power tool having an electric motor is provided. The module includes a printed circuit board (PCB), an encapsulation member forming an enclosed compartment enclosing a portion of a surface of the PCB, and power switches mounted on the surface of the PCB outside the enclosed compartment, where the power switches are electrically configured to switchably connect a supply of electric power from a power source to the electric motor. The module further includes an input unit having at least one electro-mechanical element at least partially disposed within the enclosed component and generating a signal for controlling a switching operation of the plurality of power switches.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/971,865 titled “Electronic Switch Module For A Power Tool” filed Mar.28, 2014, content of which is incorporated herein by reference in itsentirety.

BACKGROUND

Use of cordless power tools has increased dramatically in recent years.Cordless power tools provide the ease of a power assisted tool with theconvenience of cordless operation. Conventionally, cordless tools havebeen driven by Permanent Magnet (PM) brushed motors that receive DCpower from a battery assembly or converted AC power. In a PM brushedmotor, commutation is achieved mechanically via a commutator and a brushsystem. By contrast, in a brushless DC motor, commutation is achievedelectronically by controlling the flow of current to the statorwindings. A brushless DC motor includes a rotor for providing rotationalenergy and a stator for supplying a magnetic field that drives therotor. Comprising the rotor is a shaft supported by a bearing set oneach end and encircled by a permanent magnet (PM) that generates amagnetic field. The stator core mounts around the rotor maintaining anair-gap at all points except for the bearing set interface. Included inthe air-gap are sets of stator windings that are typically connected ineither a three-phase wye or Delta configuration. Each of the windings isoriented such that it lies parallel to the rotor shaft. Power devicessuch as MOSFETs are connected in series with each winding to enablepower to be selectively applied. When power is applied to a winding, theresulting current in the winding generates a magnetic field that couplesto the rotor. The magnetic field associated with the PM in the rotorassembly attempts to align itself with the stator generated magneticfield resulting in rotational movement of the rotor. A control circuitsequentially activates the individual stator coils so that the PMattached to the rotor continuously chases the advancing magnetic fieldgenerated by the stator windings. A set of sense magnets coupled to thePMs in the rotor assembly are sensed by a sensor, such as a Hall Effectsensor, to identify the current position of the rotor assembly. Propertiming of the commutation sequence is maintained by monitoring sensorsmounted on the rotor shaft or detecting magnetic field peaks or nullsassociated with the PM.

Conventionally, power switches are provided within the power tool inclose proximity to the motor or within the handle. Electronics includinga controller for controlling the power devices are also provided withinthe handle or in the vicinity of the motor. A trigger switch assembly isalso provided, preferable on the handle where it is easy for the user toengage. The controller is coupled to both the trigger assembly and thepower devices and regulates the flow of power through the power devicesbased on the input from the trigger assembly. All the connectivitybetween these modules requires substantial wiring. Also, since the powerdevices generate a considerable amount of heat, they should be arrangedwithin the power tool to transfer heat away from the power deviceseffectively.

SUMMARY

According to an aspect of the invention, an electronic switch andcontrol module is provided for a power tool having an electric motor,comprising: a module housing including a bottom surface, side walls, andan open face; a printed circuit board (PCB) fittingly received from theopen face of the module housing and securely disposed within the modulehousing; an encapsulation member arranged to mate with a mating surfaceof the side walls of the module housing to form an enclosed compartmentover a portion of the PCB to enclose at least one electronic orelectro-mechanical element mounted on a surface of the PCB; and aplurality of power switches mounted on the surface of the PCB within anopen compartment of the module housing where the encapsulation memberdoes not enclose the surface of the PCB, the power switches beingelectrically configured to switchably connect a supply of electric powerfrom a power source to the electric motor.

In an embodiment, the electronic switch and control module furtherincludes a controller mounted on the PCB and coupled to the input unitand the power switches, and the controller is configured to control theswitching operation of the power switches based the signal from theinput unit.

In an embodiment, the electronic switch and control module furtherincludes a heat sink arranged to transfer heat away from the powerswitches.

In an embodiment, the electronic switch and control module furtherincludes a plurality of heat sinks discretely mounted over a respectiveone of the plurality of power switches and secured to the surface of thePCB to transfer heat away from the power switches.

In an embodiment, the electronic switch and control module furtherincludes an input unit having at least one electro-mechanical element atleast partially disposed within the enclosed component and generating asignal for controlling a switching operation of the plurality of powerswitches.

In a further embodiment, the electro-mechanical element of the inputunit includes a speed-sensing member on the surface of the PCB and avariable-speed actuator having a sliding member in sliding contact withthe speed-sensing member, where the speed-sensing member and the slidingmember are disposed and substantially enclosed within the enclosedcompartment, and the speed-sensing member generates the signal forcontrolling a switching operation of the plurality of power switchesbased on a sliding position of the sliding member. In an embodiment, thevariable-speed actuator further includes a variable-speed triggerdisposed outside the module housing and a link slidably extending fromthe variable-speed through an aperture in the module housing into theenclosed compartment and coupled to the sliding member.

In an further or alternative embodiment, the electro-mechanical elementof the input unit includes a contact-sensing member on the surface ofthe PCB and a forward/reverse actuator having a contact member inselective contact with the contact-sensing member, where thecontact-sensing member and the contact member are disposed andsubstantially enclosed within the enclosed compartment, and thecontact-sensing member generates the signal for controlling a rotationaldirection of the motor. In an embodiment, the forward/reverse actuatorfurther includes a pivot member supported by the module housing and anengagement member extending outside the module housing from the pivotmember, the pivot member pivotably linking the contact member and theengagement member.

In an embodiment, the encapsulation member includes a wall arranged torest on the surface of the PCB, and a lower end of the wall is sealed tothe surface of the PCB.

In an embodiment, the encapsulation member includes at least one of wireretention or wire guide features arranged to retain or guide wirescoupled to the PCB.

In an embodiment, the electronic switch and control module furtherincludes a conformal coating applied on the surface of the PCBassociated with the open compartment but not on at least a part of thesurface of the PCB associated with the enclosed compartment. In afurther embodiment, the encapsulation member includes a wall arranged torest on the surface of the PCB, and a lower end of the wall is sealed tothe surface of the PCB via the conformal coating.

In an embodiment, the encapsulation member and the module housinginclude mating features for securely mounting the encapsulation memberon the module housing. In a further embodiment, the mating featuresinclude a tongue provided on one of the encapsulation member or themodule housing and a corresponding groove provided on the other of theencapsulation member or the module housing to form a seal between theencapsulation member and the module housing.

In an embodiment, an electric power tool is provided having an electricmotor and an electronic switch and control module as described above. Inan embodiment, the electric motor is a three-phase brushless DC motorand the power switches include six Field Effect Transistors connected asa three-phase bridge rectifier. In an embodiment, the electric motor isrotatably coupled to a fan inside a motor housing, and the electricpower module is disposed in a tool handle in fluid communication withthe motor such that an airflow is generated by the fan through thehandle to transfer heat away from the power switches within the opencompartment. In an embodiment, the power tool is a drill or an impactdriver. In an embodiment, the power tool includes a variable speedtrigger or a forward/reverse button engaging the input unit.

According to another aspect of the invention, an electronic switch andcontrol module for a power tool having an electric motor, comprising: aprinted circuit board (PCB); an encapsulation member forming an enclosedcompartment enclosing a portion of a surface of the PCB; a plurality ofpower switches mounted on the surface of the PCB outside the enclosedcompartment, the power switches being electrically configured toswitchably connect a supply of electric power from a power source to theelectric motor; and an input unit having at least one electro-mechanicalelement at least partially disposed within the enclosed component andgenerating a signal for controlling a switching operation of theplurality of power switches.

In an embodiment, the electronic switch and control module includes acontroller mounted on the PCB and coupled to the input unit and theplurality of power switches, and the controller is configured to controlthe switching operation of the power switches based the signal from theinput unit. In an embodiment, the controller is mounted on a backsurface of the PCB.

In an embodiment, the electronic switch and control module includes aheat sink arranged to transfer heat away from the power switches. In analternative embodiment, the electronic switch and control moduleincludes a plurality of heat sinks discretely mounted over a respectiveone of the plurality of power switches and secured to the surface of thePCB to transfer heat away from the power switches.

In an embodiment, the electro-mechanical element of the input unitincludes a speed-sensing member on the surface of the PCB and avariable-speed actuator having a sliding member in sliding contact withthe speed-sensing member, where the speed-sensing member and the slidingmember are disposed and substantially enclosed within the enclosedcompartment, and the speed-sensing member generates the signal forcontrolling a switching operation of the plurality of power switchesbased on a sliding position of the sliding member. In an embodiment, thevariable-speed actuator further includes a variable-speed triggerdisposed outside the enclosed compartment and a link slidably extendingfrom the variable-speed through an aperture in the enclosed compartmentinto the enclosed compartment and coupled to the sliding member. In anembodiment, the speed-sensing member includes a series of conductivetracks on the surface of the PCB and the variable-speed actuatorincludes a conductive wiper in sliding contact with the conductivetracks. In an embodiment, the encapsulation member includes an axialchamber facilitating a sliding movement of the sliding member andrestraining a lateral movement of sliding member away from the PCB.

In an embodiment, the electro-mechanical element of the input unitincludes a contact-sensing member on the surface of the PCB and aforward/reverse actuator having a contact member in selective contactwith the contact-sensing member, where the contact-sensing member andthe contact member are disposed and substantially enclosed within theenclosed compartment, and the contact-sensing member generates thesignal for controlling a rotational direction of the motor. In anembodiment, the forward/reverse actuator further includes a pivot membersupported by the enclosed compartment and an engagement member extendingoutside the enclosed compartment from the pivot member, the pivot memberpivotably linking the contact member and the engagement member. In anembodiment, the contact-sensing member comprises a pair of conductivetracks on the surface of the PCB and the contact member includes anelectrical connector that selectively comes into contact with none, one,or both of the conductive tracks. In an embodiment, the encapsulationmember includes a chamber facilitating a pivoting movement of thesliding member towards and away from the PCB.

In an embodiment, the electronic switch and control module furtherincludes a module housing substantially encapsulating sides and a lowersurface of the PCB. In an embodiment, the encapsulation member mateswith a mating surface of the module housing to enclose the surface ofthe PCB within the enclosed compartment.

In an embodiment, an electric power tool is provided having an electricmotor and an electronic switch and control module as described above. Inan embodiment, the electric motor is a three-phase brushless DC motorand the power switches include six Field Effect Transistors connected asa three-phase bridge rectifier. In an embodiment, the electric motor isrotatably coupled to a fan inside a motor housing, and the electricpower module is disposed in a tool handle in fluid communication withthe motor such that an airflow is generated by the fan through thehandle to transfer heat away from the power switches outside the closedcompartment. In an embodiment, the power tool is a drill or an impactdriver. In an embodiment, the power tool includes a variable speedtrigger or a forward/reverse button engaging the input unit.

According to another aspect of the invention, an electronic switch andcontrol module for a power tool having an electric motor is provided,comprising: a module housing including a bottom surface, side walls, andan open face; a printed circuit board (PCB) received from the open faceof the module housing and securely disposed within the module housing ata distance from the bottom surface of the module housing; a plurality ofpower switches mounted on a top surface of the PCB, the power switchesbeing electrically configured to switchably connect a supply of electricpower from a power source to the electric motor; a plurality of heatsinks discretely arranged and each mounted over a respective one of theplurality of power switches and secured to the top surface of the PCB totransfer heat away from the power switch through the open face of themodule housing; an input unit having a plurality of conductive tracksdisposed on the PCB and an electro-mechanical element engaging theplurality of conductive tracks, the input unit generating a signal forcontrolling a switching operation of the plurality of power switches;and a controller mounted on the PCB coupled to the plurality of powerswitches and the input unit, where the controller is configured tocontrol the switching operation of the power switches based the signalfrom the input unit.

In an embodiment, the conductive tracks are disposed on the top surfaceof the PCB.

In an embodiment, the controller is mounted on a lower surface of thePCB facing the bottom surface of the module housing, the controllerbeing electronically connected to the power switches via a plurality ofvias.

In an embodiment, the module housing includes retention features forsecurely holding the PCB at a distance from the bottom surface of themodule housing.

In an embodiment, each heat sink includes a main plate disposed directlyabove the respective power switch at close proximity thereto, and atleast one leg mounted on the PCB and electronically coupled to a drainof the respective power switch.

In an embodiment, the power switches are six Field Effect Transistors(FETs) configured as a three-phase bridge rectifier.

In an embodiment, the electronic switch and control module furtherincludes a potting compound formed around the PCB within the housing butleaves a top surface of the heat sink exposed through the open face ofthe module housing. In an embodiment, the potting compound leavesexposed a main plate of the heat sink with a surface area ofapproximately between 20 to 30 mm².

In an embodiment, the electronic switch and control module includes anencapsulation member that substantially covers the input unit andincludes a chamber housing the electro-mechanical element in engagementwith the conductive tracks. In an embodiment, the encapsulation membermates with at least one of the side walls of the module housing andincludes at least one of wire retention or wire guide features arrangedto retain or guide wires coupled to the PCB.

In an embodiment, the electronic switch and control module includes acover configured to mate with at least one of the side walls of themodule housing to partially cover a portion of the PCB not including anarea of the PCB where the plurality of power switches and plurality ofheat sinks are mounted. In an embodiment, the cover includes at leastone of wire retention or wire guide features arranged to retain or guidewires coupled to the PCB.

In an embodiment, an electric power tool is provided having an electricmotor and an electronic switch and control module as described above. Inan embodiment, the electric motor is a three-phase brushless DC motorand the power switches include six Field Effect Transistors connected asa three-phase bridge rectifier. In an embodiment, the electric motor isrotatably coupled to a fan inside a motor housing, and the electricpower module is disposed in a tool handle in fluid communication withthe motor such that an airflow is generated by the fan through thehandle to transfer heat away from the power switches within the opencompartment.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will become more fullyunderstood from the detailed description given herein below and theaccompanying drawings, wherein like elements are represented by likereference numerals, which are given by way of illustration only and thusare not limitative of the example embodiments of the present invention.

FIG. 1 depicts a longitudinal cross-sectional view of a power tool witha housing half removed, according to an embodiment;

FIGS. 2A and 2B depict perspective views of an electronic control modulefrom two different angles, according to an embodiment;

FIGS. 3A and 3B respectively depict expanded front and back perspectiveviews of the electronic control module, according to an embodiment;

FIGS. 4A and 4B respectively depict a zoomed-in perspective view and across-sectional view of a the electronic control module showing thearrangement of a power switch and a heat sink on a printed circuit board(PCB), according to an embodiment;

FIG. 5 depicts a top view of the PCB alone without any mountedcomponents, according to an embodiment;

FIG. 6 depicts a partial perspective view of the electronic controlmodule showing an encapsulation member sealed over the PCB, according toan embodiment;

FIG. 7 depicts a partial perspective view of the electronic controlmodule showing mating features for mounting the encapsulation member tothe control module housing, according to an embodiment;

FIGS. 8A and 8B depict side and perspective views of a biasing member(forward/reverse spring), according to an embodiment;

FIGS. 9A-9C depict cross-sectional views of a forward/reverse actuatorrelative to the biasing member in forward, locked, and reversepositions, respectively, according to an embodiment;

FIG. 10 depicts a partial perspective view of the electronic controlmodule without the encapsulation member, according to an embodiment;

FIG. 11 depicts a cross-sectional view of the variable-speed actuatorwithin the enclosed compartment, according to an embodiment; and

FIG. 12 depicts a zoomed-in view of a post for the variable-speedcompression spring, according to an embodiment.

DESCRIPTION

With reference to the FIG. 1, a power tool 100 constructed in accordancewith the teachings of the present disclosure is illustrated in alongitudinal cross-section view. Power tool 100 in the particularexample provided may be a hand held impact driver, but it will beappreciated that the teachings of this disclosure is merely exemplaryand the power tool of this invention could be any power tool. The powertool shown in FIG. 1 may include a housing 102, an electric motor 104, abattery pack 108, a transmission assembly (gear case) 114, and an outputspindle 116. The gear case 114 may be removably coupled to the housing102. The housing 102 can define a motor housing 111 and a handle 112.

According to an embodiment, motor 104 is received in motor housing 111.Motor 104 may be be any type of motor and may be powered by anappropriate power source (electricity, pneumatic power, hydraulicpower). In an embodiment, the motor is a brushless DC electric motor andis powered by a battery pack 108.

According to an embodiment of the invention, power tool 100 furtherincludes an integrated electronic switch and control module 200(hereinafter referred to as “electronic control module”, or “controlmodule”). Electronic control module 200, in an embodiment, may include acontroller and electronic switching components for regulating the supplyof power from the battery pack 108 to motor 105. In an embodiment,electronic control module 200 is disposed within the handle 112 belowthe motor housing 111, though it must be understood that depend on thepower tool shape and specifications, electronic control module 200 maybe disposed at any location within the power tool. Electronic controlmodule may also integrally include components to support a user-actuatedinput unit 110 (hereinafter referred to as “input unit” 110) forreceiving user functions, such as an on/off signal, variable-speedsignal, and forward-reverse signal. In an embodiment, input unit 100 mayinclude a variable-speed trigger 120, although other input mechanismsuch as a touch-sensor, a capacitive-sensor, a speed dial, etc. may alsobe utilized. In an embodiment, an on/off signal is generated uponinitial actuation of the variable-speed trigger 120. In an embodiment, aforward/reverse button 122 is additionally provided on the tool 100. Theforward/reverse button 122 may be pressed on either side of the tool ina forward, locked, or reverse position. In an embodiment, the associatedcircuitry and components of the input unit 110 that support thevariable-speed trigger 120 and the forward/reverse button 122 may befully or at least partially integrated into the electronic controlmodule 200. Based on the input signals from the input unit 110 andassociated components, the controller and electronic switchingcomponents of the electronic control module 200 modulate and regulatethe supply of power from the battery pack 108 to motor 105. Details ofthe electronic control module 200 are discussed later in detail.

While in this embodiment, the power source is battery pack 108, it isenvisioned that the teachings of this disclosures may be applied to apower tool with an AC power source. Such a power tool may include, forexample, a rectifier circuit coupled to the AC power source.

It must be understood that, while FIG. 1 illustrates a power tool impactdriver having a brushless motor, the teachings of this disclosure may beused in any power tool, including, but not limited to, drills, saws,nailers, fasteners, impact wrenches, grinders, sanders, cutters, etc.Also, teachings of this disclosure may be used in any other type of toolor product that include a rotary electric motor, including, but notlimited to, mowers, string trimmers, vacuums, blowers, sweepers, edgers,etc.

The electronic control module 200 is described herein, according to anembodiment of the invention. FIGS. 2A and 2B depict perspective views ofelectronic control module 200 from two different angles, according to anembodiment. FIGS. 3A and 3B depict exploded front and back views of thesame module 200, according to an embodiment. Reference is made to thesedrawings herein.

Electronic control module 200, in an embodiment, includes a printedcircuit board (PCB) 202 arranged and mounted inside a module housing204. Module housing 204 includes a bottom surface 227, side walls 228,and an open face. PCB 202 is inserted through the open face and securedinside the module housing 204. Side walls 228 include retention features229 for securely holding the PCB 202 at a distance from the bottomsurface 227. Control module 200 includes two compartments—an enclosedcompartment 210 a that houses and encloses a first part of the PCB 202and components associated with the input unit 110, as described below,and an open compartment 210 b, and partially encloses a second part ofthe PCB 202. Within the open compartment 210 b, module housing 204encloses the lower surface and the sides of PCB 202, but leaves theupper surface of the PCB 202 substantially exposed. Mounted on the uppersurface of PCB 202 are a series of power switches 206 and a series ofheat sinks disposed over the power switches 206 and secured to the PCB202. As discussed below in detail, this arrangement allows cooling airto transfer heat away from the heat sinks 208 within the power tool 100,but protects the input unit 110 components from any dust and debris fromthe cooling air.

According to an embodiment, control module 200 includes a controller218. In an embodiment, the controller may be mounted to a lower surfaceof the PCB 202 and be in electronic communication with the rest of thePCB 202 components through vias (not shown). In an embodiment,controller 218 may be a programmable micro-controller, micro-processor,or other processing unit capable of controlling the motor and variousaspects of power tool. For example, controller 218 may be programmed toturn on and off power switches 206, as discussed below, to controlcommutation of the brushless motor. In an embodiment, controller 218 maybe coupled to a series of gate drivers disposed on the PCB 202, which inturn are connected to the gates of the power switches 206.Alternatively, controller 218 may be a circuit chip that includes both amicro-controller and the gate drivers and be coupled directly to thegates of the power switches 206. Using the gate drivers, controller 218turns the power switches 206 on or off selectively to commutate themotor and control the speed of the motor. Additionally, the controllermay be programmed to various tool and battery pack operation features,such as tool and/or temperature control, battery pack voltage control,and tool over-current detection and control, etc. In an alternativeembodiment, the controller may be an Application Specific IntegratedCircuit (ASIC) configured to control the aforementioned aspects of themotor, battery, and power tool.

In an exemplary embodiment, power switches 206 may be Field EffectTransistors (FETs). In an embodiment, six power switches 206, includingthree high-side power switches and three low-side power switches, arearranged and coupled together as a three-phase bridge rectifier circuit.Using the gate drivers, controller 218 sequentially turns the powerswitches 206 on and off within each phase of the brush motor 104commutation. Further, the controller 218 performs pulse-width modulation(PWM) of the power switches 206 within each phase to regulate the speedof the motor based on speed signals received from input unit 110, asdescribed below. Controller 218 further controls the direction of motorcommutation based on a forward/reverse signal received from input unit110, also discussed below.

It is noted that while the power switches 206 discussed herein are FETs,other types of power switches such as BJTs or IGBTs may be utilized.Additionally, while power switches 206 are arranged as a three-phasebridge rectifier for driving a three-phase brushless motor, other numberand arrangement of power switches may be used to drive other types ofmotors, including brushed or brushless motors.

As described above, module housing 204 leaves the upper surface of thePCB 202 exposed, thus allowing heat to dissipate from the heat sinks208. Electronic control module 200 may be placed within a path of airflow inside the power tool, e.g., inside the power tool handle 112 influid communication with motor fan 106 so that airflow generated bymotor fan 106 runs through the handle 112. The air flow generated withinthe handle further improves heat dissipation from the electronic controlmodule 200.

In an embodiment, the PCB 202 is further potted with a layer of pottingcompound (not shown) in the open compartment 210 b. The layer of pottingcompound, in an embodiment, substantially covers most of the circuitcomponents on the PCB, but leave a top plate of heat sinks 206 exposedso the heat sinks 208 can dissipate heat away from the power switches206. While the potting compound is not shown in FIGS. 2A-3B, the controlmodule of FIG. 1 is shows with the potting compound disposed inside thehousing 202.

FIGS. 4A and 4B depict zoomed-in perspective and cross-sectional viewsof PCB 202, showing the arrangement of heat sink 208 and power switch206 (in this case a FET) mounted over PCB 202, according to anembodiment. Heat sink 208 includes two legs mounted on the PCB 202. Themain plate of heat sink 208 is located directly above power switch 206at close proximity thereto. This allows heat to be transferred directlyfrom power switch 206 to the heat sink 208 through a small air gapbetween the two. In an embodiment, the main plate of the heat sink 208has a surface area of 10 to 40 mm², preferably 15-35 mm², morepreferably 20-30 mm², that is exposed after the potting compound isapplied. In addition, one or more of the legs of the heat sink 208 iselectrically connected to the drain of power switch 206 on the PCB 202.This arrangement further improves heat transfer from the FET 206 to theheat sink 208.

It is noted that while in this embodiment discrete heat sinks 208 aremounted on respective power switches 206, a lower number of heat sinks208 may be utilized instead. In an alternative embodiment of theinvention, a single heat sink is mounted on the PCB over the powerswitches 206 to provide a higher surface area for heat transfer.

Referring back to FIGS. 2A through 3B, in an embodiment, a series ofoutput wires 212 are secured on one end to a surface of the PCB 202.These wires connect the outputs of the power switches three-phase bridgerectifier to the power terminals the brushless motor 104. In anembodiment, a series of control signal wires 214 are also secured to awire receptacle 215 a. In an embodiment, wire receptacle 215 a ismounted on the PCB and is in electrical communication with thecontroller 218. The control signal wires 214 allow the controller 218 tocommunicate with other parts of the power tool 100, such as the motor104 and the battery 108. In an embodiment, hall signals from thebrushless motor hall sensors communicate with the controller 218 throughthese control signal wires 214. Control signal wires 214 mayadditionally be provided with a control terminal 215 b to ease plug-inconnectivity of external wires with the control signal wires 214. In anembodiment, a pair of power input wires 217 are also secured on thesurface of PCB 202. These wires are coupled to a power source (e.g.,battery 108) via a power terminal 216 to supply power from the powersource to the power switches 206.

In an embodiment, control module 200 includes an encapsulation member260 that mates with the module housing 204 to form the enclosedcompartment 210 a of control module 200. As discussed below in detail,encapsulation member 260 protects components associated with input unit110 from dust and debris. Encapsulation member 260 also includes wireretaining features 262 and wire guide features 264 for retaining andpositioning signal wires 214 and/or power output wires 212 away from thehousing 204. Encapsulation member 260 further includes mating features266 that mate with corresponding mating features 268 on the modulehousing 204. In an embodiment, the mating features 268 include lips thatsnap fit into slots in mating features 266. In an embodiment,encapsulation member 260 further includes an opening 269 that allowscontrol signal wires 214 to connect to PCB-side control terminal 215 a.

Additionally, in an embodiment, control module 200 includes anadditional cover 270 that covers a lower portion of PCB 202. Cover 270also includes wire retaining features 272 for retaining the power wires217, as well as wire guide features 274 for guiding the wires 217 aroundcircuit components (e.g., capacitors 280) mounted on PCB 202. Cover 270further includes mating features 276 that mate with corresponding matingfeatures 278 on the module housing 204. In an embodiment, the matingfeatures 278 include lips that snap-fit into slots in mating features276.

In an embodiment, control module 200 is additionally provided with anauxiliary control terminal 252 mounted on a top portion of the PCB 202that allows the controller 218 with other motor or tool components. Inan embodiment, auxiliary control terminal 252 allows the controller 218to communicate with an LED provided on the tool 100. In an embodiment,auxiliary control terminal 252 is provided outside and adjacent to theenclosed compartment 210 a.

The input unit 110 is discussed herein, according to an embodiment ofthe invention. According to an embodiment, input unit 110 is at leastpartially integrated into control module 200. In an embodiment, inputunit 110 incorporates electro-mechanical elements for variable-speeddetection, on/off detection, and forward/reverse detection inside theenclosed compartment 210 a of control module 200, as discussed herein.

In an embodiment, input unit 110 includes a forward/reverse actuator 220supported by the enclosed compartment 210 a portion of the modulehousing 204. In an embodiment, forward/reverse actuator 220 includes acontact member 220 a, which holds an electrical connector 222 and isdisposed inside the enclosed compartment 210 a of the module housing204, and an engagement member 220 b, which is located outside the modulehousing 204. In an embodiment, engagement member 220 b is in movingcontact with forward/reverse button 122 on the power tool 100. A pivotmember 220 c located between the contact member 220 a and engagementmember 220 b is supported by the module housing 204 and provides a pivotpoint for the forward/reverse actuator. A biasing member 224 is securedto the module housing 204 to engage and bias the contact member 220 a ina forward, neutral (e.g., locked), or reverse direction. In anembodiment, biasing member 224 is secured in an opening of a holder,i.e. a post 226 that projects from the bottom surface 227 of the modulehousing 204 within the enclosed compartment 210 a. In an embodiment, PCB202 is provided with a through-hole 254 that receives the post 226. Whenthe user presses the forward/reverse button 122 from either side of thetool to a forward, locked, or reverse position, the forward/reversebutton 122 moves the engagement member 220 around the pivot portion 220c. Pivoting movement of the engagement member 220 b around the pivotportion 220 c causes the electrical connector 222 of contact member 220a to make or break contact with a contact-sensing member against thebiasing force of the biasing member 224. In an embodiment, contact sensemember includes a pair of conductive tracks 250 arranged on PCB 202.

In an embodiment, one of the conductive tracks 250 is electricallyconnected to power source 108 and the other is connected to and sensedby controller 218. Voltage is present and sensed by the controller 218when electrical connector 222 makes contact with the pair of conductivetracks 250, thus electrically connecting the two conductive tracks 250.Presence or lack of sensed voltage is indicative of whether the motorshould rotate in the forward or reverse direction. Functional details ofuse and electrical connectivity of conductive tracks 250 forforward/reserve detection are discuss in co-pending Patent Publicationno. 2012/0292063 filed May 21, 2012, which is incorporated herein byreference in its entirety.

According to an embodiment, input unit 110 further includes avariable-speed actuator 230. Variable-speed actuator includes a linkmember 232 that extends out of the module housing 204 from a slidingmember 234 that is arranged inside the module housing 204 and supports aconductive wiper 236. Link member 232 is coupled to trigger 120 that isengageable by the user. The sliding member 234 supports and engages acompression spring 238 its longitudinal end opposite link member 232.Compression spring 238 is located between an inner wall of the modulehousing 204 and the sliding member 234. When the user presses thetrigger 120, the sliding member 234 moves against a biasing force of thespring 238.

Conductive wiper 236 contacts a speed-sensing member located on thesurface of the PCB 202. In an embodiment, the speed-sensing member is aseries of variable-speed conductive tracks 240 arranged on the PCB 202.Actuation of the trigger 120 moves the conductive wiper 236 over theconductive tracks 240. Initial movement of the conductive wiper 236 overthe conductive tracks 240 generates a signal that turns controller 218ON. Additionally, an analog variable-voltage signal is generated basedon the movement of the conductive wiper 128 over the conductive tracksand that signal is sent to the micro-controller. This signal isindicative of the desired motor speed. Functional details of ON/OFF andvariable-speed detection using conductive tracks 240 are discuss inco-pending Patent Publication no. 2012/0292063 filed May 21, 2012, whichis incorporated herein by reference in its entirety. It must beunderstood, however, that any known variable-voltage speed-sensingmechanism, such as a resistive tape, may be a utilized within the scopeof the invention.

It is noted that the moving mechanical parts of the forward/reverseactuator 220 and variable-speed actuator 230 (including the electricalconnector 222 and conductive wiper 236), alone or in combination withconductive tracks 240 and 250, are referred to in this disclosure as“electro-mechanical” elements.

FIG. 5 depicts a top view of PCB 202 alone without any componentsmounted. As shown herein, PCB 202 is provided with metal traces 282 formounting the power switches 206, as well as variable-speed conductivetracks 240 and forward/reverse conductive 250. Through-hole 254 andauxiliary terminal 252 is also shown in this figure.

In an embodiment, a layer of silicon conformal coating is applied to thePCB 202 to protect it from dust, debris, moisture, and extremetemperature changes. However, since the conductive tracks 250 and 240need to remain exposed to make electrical contact with theforward/reverse electrical connector 222 and variable-speed conductivewiper 236, a high temperature resistant tape 284 is applied to the PCB202 over the conductive tracks 240 and 250 before the silicon conformalcoating is applied. The high temperature resistant tape 284 ensures thatthe silicon conformal coating does not cover the conductive tracks 240and 250.

In an embodiment, since no conformal coating is provided to protect theconductive tracks 250 and 240, conductive tracks 250 and 240 are proneto damage from debris, contamination, and moisture. In addition,electro-mechanical components of the input unit (i.e., forward/reverseactuator 220 and variable-speed actuator 230, particularlyforward/reverse electrical connector 222 and variable-speed conductivewiper 236) are also similarly prone to damage or faulty contact with theconductive tracks 200 and 250. For this reason, the conductive tracks250 and 240 and the electro-mechanical elements of the input unit 110are arranged inside the enclosed compartment 210 a of the control module200, where the encapsulation member 260 mates with the module housing204 to seal and protect these components from dust, contamination,and/or moisture. In an embodiment, encapsulation member 260substantially encloses the area 284 around the conductive tracks 250 and240. In an embodiment, encapsulation member also encloses the spacearound the electro-mechanical components including contact member 220 aof the forward/reverse actuator 220, sliding member 234 of thevariable-speed actuator 230, spring 238, etc.

Referring back to FIGS. 3A and 3C, in an embodiment, mating surfaces ofencapsulation member 260 and module housing 204 includes supportfeatures 286 a, 286 b that receive and support link member 232 ofvariable-speed actuator 230, forming an aperture for the link member 232to slidably extend out of the module housing 204. In an embodiment, thelink member 232 is laterally secured in the aperture via one or morerings 233. Similarly, mating surfaces of encapsulation member 260 andmodule housing 204 includes pivot support features 288 a, 288 b thatreceive and support pivot member 220 c of forward/reverse actuator 220,forming an aperture for the engagement member 220 b of theforward/reverse actuator 220 to extend out of the module housing 204.

In an embodiment, encapsulation member 260 not only protects the inputunit 110 from dust and contamination, it also acts as a mechanicalconstrain for its mechanical components. In an embodiment, encapsulationmember 260 includes a first chamber 290 that houses the sliding member234 and compression spring 238 of the variable-speed actuator 230, and asecond chamber 292 that houses the contact member 220 a of theforward/reverse actuator 220. The first chamber 290 forms an axialchannel for the back and forth movement of the sliding member 234 andmechanically restrains its lateral movement. In an embodiment, thisarrangement ensures that there is always contact between the wiper 236and the conductive tracks 240. Similarly, the second chamber 290facilitates the pivoting movement of the forward/reverse actuator 220.

Referring now to FIGS. 6 and 7, additional features for sealing theenclosed compartment 210 a from outside contamination are discussedherein, according to an embodiment.

As shown in FIG. 6, according to an embodiment, encapsulation member 260includes a wall 294 arranged to rest on the PCB 202 when theencapsulation member 260 is mounted in order to fully enclose theenclosed compartment 210 a, in an embodiment. In an embodiment, anadhesive may be applied to block any gaps between the wall 294 and thePCB 202. Alternatively, in an embodiment, during the assembly process,encapsulation member 260 is mounted on the module housing 204immediately or shortly after conformal coating 295 is applied to PCB202, preferably prior to conformal coating 295 cooing down. In thismanner, once conformal coating 295 is cooled and hardened, it acts as aseal between the wall 294 of the encapsulation member 260 and the PCB202.

As shown in FIG. 7, and as discussed above, encapsulation member 260further includes mating features 266 that mate with corresponding matingfeatures 268 on the module housing 204. In an embodiment, matingsurfaces of encapsulation member 260 and module housing 204 areadditionally respectively provided with tongue 296 and groove 298features to seal the mating surfaces of encapsulation member 260 and thehousing 204 and block or reduce entry of dust or contamination into theenclosed compartment 210 a.

While exemplary embodiments of the invention are discussed withreference to a module housing 204, it must be understood that thecompartmental concepts of the invention for sealing theelectro-mechanical components associated with the input unit 101components while leaving the power switches 206 exposed may be appliedto alternative embodiments. For example, it is envisioned that a PCB 202is disposed within a tool housing 102 without a separate module housing204. In that case, an encapsulation member may be provided to around theenclosed compartment 210 a of the PCB 202, with walls mounted and sealedto both surfaces of the PCB 202. Alternatively, encapsulation member maybe mounted directly on the PCB 202 without a need for a separate modulehousing 204. It is also envisioned that in some alternative embodiments,the enclosed compartment 210 a is formed by an integral part of the toolhousing 204 rather than a separate piece.

Another aspect of the invention is described herein with reference toFIGS. 8 and 9A-9C.

As described above, most power tools used for drilling and cuttingoperations need to be operated in both forward and reverse directions.The forward/reverse actuator 220 described above is provided for thatpurpose. Moreover, in an embodiment, the forward/reverse actuator 220may be provided with a third setting—a locked position—to secure lockthe power tool system from running inadvertently. Effective, repeatableand reliable positional control of the contact member 220 a (hereinafteralso referred to as “lever” 220 a) is needed to provide all threefunctions (i.e., forward run, reverse run, and lock). In an embodiment,this position control is provided by biasing member 224 (herein alsoreferred to as forward/reverse spring 224), described herein.

In an embodiment, forward/reverse spring 224 includes a lever engagingmember 302 that includes upper and lower portions 302 a and 302 b with agroove formed 302 c therebetween. In an embodiment, the upper and lowerportions 302 a, 302 b are arranged at an obtuse angle 8 of approximately120 to 150 degrees with respect to one another. The groove 302 c isformed at the end common point (vertex) of the angle between the upperand lower portions 302 a, 302 b, towards the interior of the angle. Thelever engaging member 302 engages a contact tip 300 of lever 220 a ofthe forward/reverse actuator 220 to bias the forward/reverse actuator220 in a forward (FIG. 9A), locked (FIG. 9B), or reverse (FIG. 9C)positions. Extending longitudinally from an end of upper portion 302 ais an extension portion 304 that is substantially horizontal withrespect to a plane of the PCB 202. A first leg 306 extends downwardlyfrom an end of the extension portion 304 at close to a right angle.First leg 306 is securely places in an opening between first and secondwalls 320, 322 of post 226 projecting from a bottom surface 227 of themodule housing 204. In an embodiment, first leg 306 includes an angularrib 308 that engages first wall 320 to secure the first leg 306 withinthe opening. In an embodiment, first leg 306 also includes a humpedsurface 310 that is pressed against the first wall 320 to providefurther stability. In an embodiment, extending from an end of the lowerportion 302 b is a second leg 312 folding inwardly and positionedbetween the lever engaging member 302 and the first leg 306. In anembodiment, the second leg 312 extends upwardly along an axis that isless than parallel to an axis of the first leg 306 (e.g., where the twoaxes for an angle of less than 20 degrees, preferably less than 10degrees). When assembled, second leg 312 engages an outer face of secondwall 322 of the post 226. Second leg 312 includes a contact portion 314that makes contact with the outer face of second wall 322, in anembodiment.

As shown in FIG. 9A, in a forward direction, contact tip 300 engages theupper portion 302 a of the lever engaging member 302 and is biased awayfrom the PCB 202. In this position, the biasing force is applied by theupper portion 302 a and a top of the first leg 306 of theforward/reverse spring 224, which is resiliently forced towards thefirst wall 320. The second leg 312 in this position has minimal or nocontact with the second wall 322 and thus applies less biasing force onthe contact tip 300.

As shown in FIG. 9B, as the forward/reverse actuator 220 is pivoted tothe locked position, contact tip 300 slides down the upper portion 302 auntil it reaches the groove 302 c of the lever engaging member 302. Asthe contact tip 300 slides down, the biasing force on the contact tip300 is applied by both the first and second legs 306 and 312 against thefirst and second walls 320 and 322, respectively. When in the lockedposition, in an embodiment, only one leg of the electrical connector 222is in contact with the PCB 202.

As shown in FIG. 9C, as the forward/reverse actuator 220 is pivoted tothe reverse position, contact tip 300 slides down from the groove 302 cover the lower portion 302 b of the lever engaging member 302. As thecontact tip 300 slides down, the biasing force on the contact tip 300 isapplied mostly by the second legs 312, which comes into substantialcontact with the second wall 322. When in the reverse position, in anembodiment, both legs of the electrical connector 222 are in contactwith the conductive tracks 250 on the PCB 202, which send a voltagesignal to the controller 218 indicative of the reverse position.

It is noted that forward/reverse spring 224 is very easy to assembleinto the housing 204. Whereas conventional designs required complicatedretention features and precision assembly, assembling theforward/reverse spring 224 simply involves insertion of the first leg306 into the post 226 opening.

In an embodiment, each leg of the electrical connector 222 includes acurved profile, as shown in FIGS. 9A-9C. This profile allows theelectrical connector 222 to have a smoother transition as it makescontact and slides over the conductive tracks 250 of the PCB 202.

FIG. 10 provides a zoomed-in view depicting the arrangement of theforward/reverse actuator 220 and forward/reverse spring 224 within thehousing 204, according to an embodiment.

Another aspect of the invention is described herein with reference toFIGS. 10-12. As discussed above, compression spring 238, sliding member234, and link member 232 of the variable-speed actuator 230 are enclosedby encapsulation member 260. During the assembly process, the spring 238is at least partially compressed to allow its first end to engage thesliding member 234 and its second end to engage another restrainingmember, such as an inner wall of the housing 204. Since the spring 238has to be left in its partially-compressed state, it is difficult tohold spring 238 down in place while the encapsulation cover 240 ismounted on the module housing 204 as the spring 238 tends to spring outof place.

To solve this problem, according to an embodiment of the invention, aspring post 244 is provided on the inner wall of the housing 204 wherean end of the compression spring 238 makes contact. In an embodiment, apocket 245 is additionally provided as a recess within the inner wall ofthe module housing 204 and the post 244 projects from a center of thepocket 245. In other words, the pocket 245 forms as a halo around thepost 244. FIG. 11 provides a cross-sectional view of the spring 234engaging the post 244 and pocket 245. FIG. 12 provides a zoomed-in viewof the post 244 and pocket 245. An end of the compression spring 238 isplaces around the spring post 244 within the pocket 245 during theassembly process. Post 244 and pocket 245 prevent the end of the spring238 from moving around and springing out of position. In particular, inan embodiment, post 244 fits form-fittingly inside the inner diameter ofthe compression spring 238, while the compression spring fitsform-fittingly inside the pocket 245.

In an embodiment, post 244 includes a lower surface 248 that projectssubstantially longitudinally and an upper surface 249 that is slantedaway from the inner wall of the housing 204. The lower surface 248 ofthe post helps retain the spring 238 in place along its longitudinalaxis and blocks the spring 238 from springing upward, while the uppersurface 249 provides for easier assembly of the spring 238 over the post244, i.e., by sliding the spring 238 over the post 244.

In addition, in an embodiment, sliding member 234 is also provided witha pocket 246. The other end of the spring 238 is received inside thepocket 246 of the sliding member 234. The pocket 246 also prevents thespring 238 from moving around and springing out of position.

The combination of the sliding member pocket 246, post 244, and postpocket 245 decrease the degree of freedom of compression spring 238during the assembly process. Constraining the motion of compressionspring 238 during the assembly process makes the control module 200assembly easy and decreases the time required for the assembly.

The example embodiments of the present invention being thus described,it will be obvious that the same may be varied in many ways. Suchvariations are not to be regarded as departure from the spirit and scopeof the example embodiments of the present invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. An electronic switch and control module for a power tool having anelectric motor, comprising: a printed circuit board (PCB); anencapsulation member forming an enclosed compartment enclosing a portionof a surface of the PCB; a plurality of power switches mounted on thesurface of the PCB outside the enclosed compartment, the power switchesbeing electrically configured to switchably connect a supply of electricpower from a power source to the electric motor; and an input unithaving at least one electro-mechanical element at least partiallydisposed within the enclosed component and generating a signal forcontrolling a switching operation of the plurality of power switches. 2.The electronic switch and control module of claim 1, further comprisinga controller mounted on the PCB and coupled to the input unit and theplurality of power switches, the controller being configured to controlthe switching operation of the power switches based the signal from theinput unit.
 3. The electronic switch and control module of claim 2,wherein the controller is mounted on a back surface of the PCB.
 4. Theelectronic switch and control module of claim 1, further comprising aheat sink arranged to transfer heat away from the power switches.
 5. Theelectronic switch and control module of claim 1, further comprising aplurality of heat sinks discretely mounted over a respective one of theplurality of power switches and secured to the surface of the PCB totransfer heat away from the power switches.
 6. The electronic switch andcontrol module of claim 1, wherein the electro-mechanical element of theinput unit includes a speed-sensing member on the surface of the PCB anda variable-speed actuator having a sliding member in sliding contactwith the speed-sensing member, wherein the speed-sensing member and thesliding member are disposed and substantially enclosed within theenclosed compartment, and the speed-sensing member generates the signalfor controlling a switching operation of the plurality of power switchesbased on a sliding position of the sliding member.
 7. The electric powermodule of claim 6, wherein the variable-speed actuator further includesa variable-speed trigger disposed outside the enclosed compartment and alink slidably extending from the variable-speed through an aperture inthe enclosed compartment into the enclosed compartment and coupled tothe sliding member.
 8. The electronic switch and control module of claim6, wherein the speed-sensing member comprises a series of conductivetracks on the surface of the PCB and the variable-speed actuatorincludes a conductive wiper in sliding contact with the conductivetracks.
 9. The electronic switch and control module of claim 6, whereinthe encapsulation member includes an axial chamber facilitating asliding movement of the sliding member and restraining a lateralmovement of sliding member away from the PCB.
 10. The electronic switchand control module of claim 1, wherein the electro-mechanical element ofthe input unit includes a contact-sensing member on the surface of thePCB and a forward/reverse actuator having a contact member in selectivecontact with the contact-sensing member, wherein the contact-sensingmember and the contact member are disposed and substantially enclosedwithin the enclosed compartment, and the contact-sensing membergenerates the signal for controlling a rotational direction of themotor.
 11. The electronic switch and control module of claim 10, whereinthe forward/reverse actuator further includes a pivot member supportedby the enclosed compartment and an engagement member extending outsidethe enclosed compartment from the pivot member, the pivot memberpivotably linking the contact member and the engagement member.
 12. Theelectronic switch and control module of claim 10, wherein thecontact-sensing member comprises a pair of conductive tracks on thesurface of the PCB and the contact member includes an electricalconnector that selectively comes into contact with none, one, or both ofthe conductive tracks.
 13. The electronic switch and control module ofclaim 6, wherein the encapsulation member includes a chamberfacilitating a pivoting movement of the sliding member towards and awayfrom the PCB.
 14. The electronic switch and control module of claim 1,further comprising a module housing substantially encapsulating sidesand a lower surface of the PCB.
 15. The electronic switch and controlmodule of claim 14, wherein the encapsulation member mates with a matingsurface of the module housing to enclose the surface of the PCB withinthe enclosed compartment.
 16. An electric power tool comprising: anelectric motor; and an electronic switch and control module according toclaim
 1. 17. The power tool of claim 16, wherein the electric motor is athree-phase brushless DC motor and the power switches include six FieldEffect Transistors connected as a three-phase bridge rectifier.
 18. Thepower tool of claim 16, wherein the electric motor is rotatably coupledto a fan inside a motor housing, and the electric power module isdisposed in a tool handle in fluid communication with the motor suchthat an airflow is generated by the fan through the handle to transferheat away from the power switches outside the closed compartment. 19.The power tool of claim 16 comprising a drill or an impact driver. 20.The power tool of claim 16, comprising at least one of a variable speedtrigger or a forward/reverse button engaging the input unit.